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TLV320DAC3203EVM-K: Register settings for MICBIAS

gustavo zarba
Expert 1110 points
Part Number: TLV320DAC3203EVM-K
Other Parts Discussed in Thread: TLV320DAC3203

Hi dear people,

continuing with my project using the TLV320DAC3203, I have some questions related to MICBIAS settings:

On the TLV320DAC3203 Applications Reference Guide I can read the following:

Page 1 / Register 51: MICBIAS Configuration Register
BIT       READ/WRITE         RESETVALUE      DESCRIPTION

D7             R                                 0                   Reserved. Write only default value.
D6             R/W                             0                   0: MICBIAS powered down
                                                                          1: MICBIAS powered up                
D5-D4        R/W                          00                  MICBIAS Output Voltage Configuration
                                                                         00: MICBIAS = 1.04V (CM=0.75V) or MICBIAS = 1.25V(CM=0.9V)
                                                                         01: MICBIAS = 1.425V(CM=0.75V) or MICBIAS = 1.7V(CM=0.9V)
                                                                        10: MICBIAS = 2.075V(CM=0.75V) or MICBIAS = 2.5V(CM=0.9V)
                                                                        11: MICBIAS is switch to power suppl
D3             R/W                           0                    0: MICBIAS voltage is generated from AVDD
                                                                          1: MICBIAS voltage is generated from LDOIN
D2-D0        R                            000                   Reserved. Write only default value

However, the GUI of the EVM sets D3 to 1 when I select AVDD as source for MICBIAS

Question 1: Which one is the good setting? Is the information on the data sheet wrong?

The other questions are related to Table 2-12 on P. 33 of the Reference Guide, for the MICBIAS Voltage Control:

here not only Page 1 Reg 51 is being used, but also Page 1 Reg 10 (Common Mode Control Register)

I can also read on pages 34 and 48:

"The common-mode voltage setting of the device is determined by the available analog power supply.
This common-mode (input common-mode) value is common across the ADC, DAC and analog bypass path.
The output common-mode setting is determined by the available analog power supplies (AVDD and ) and
the desired output-signal swing."

However, I can not really understand how to apply this.

In my setting, I have two dig mics from Knowles with PDM Output accepting up to 3.6V Supply Voltage, while typical would be 1.8V, being 1.6V the MIn.
My intention is (or was), to feed the mics with MICBIAS, hoping for a better Noise-Signal ratio.

The EVM is working with 3.3V. This is ok for my testing.
For my final setting, with my own hardware, I need everything to work with 2V (I had planned to use 1.8V, but the MCU won't start, so I made a compromise)
The DAC3203 is becomming those 2V on AVDD, DVDD, IOVDD and LDOIN
The output of the DAC goes to HPL and HPR

Question 2: Would you advice to feed the mics directly with the VDD Power of the system, instead of going via MICBIAS, or can I use MICBIAS to lower the Supply for the mics?

Question 3: What would be the difference regarding noise, for instance, for the TLV320DAC3203 to work with, since the digital signal of the mics would be lower as the Supply?

Thanks in advance for your help!

Best regards,

Gustavo

  • 0
    TI__Guru** 104125 points

    Hi Gustavo,

    I'll check on your questions and provide some answers by tomorrow morning.

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • +1
    TI__Guru** 104125 points

    Hi Gustavo,

    Adding comments on each question below:

    1. The information in the reference guide should be OK, and it should match what the GUI does. I checked this on my side and the GUI seems to follow the documentation. It writes w 30 33 00 for AVDD and w 30 33 08 for LDOIN.
    2. It is usually recommended to use MICBIAS to power the mics. This helps to provide a cleaner supply and it should help regardless of changing the supply level.
    3. It comes down to the mic SNR and PSRR, but usually supplying with MICBIAS provides better reference voltage for the mics, thus enabling better system performance overall. I'm not clear on the question about "would be lower as the supply", you can set MICBIAS to be same as AVDD or LDOIN, which in this case I think is the same as 2V. Is there a reason to set a different voltage level for the mics?

    Best regards,
    -Ivan Salazar
    Applications Engineer

  • 0 in reply to Ivan Salazar
    Expert 1110 points

    Hi Ivan,
    you have answered my questions, thanks!
    And no, there is no reason to have a different voltage level for the mics. I was not sure about setting the MICBIAS = LDOIN. Now is clear.
    Best regards,
    Gustavo